The cellular telephone industry has had an enormous development in the world in the past decades. From the initial analog systems, such as those defined by the standards AMPS (Advanced Mobile Phone System) and NMT (Nordic Mobile Telephone), the development has during recent years been almost exclusively focused on standards for digital solutions for cellular radio network systems, such as D-AMPS (e.g., as specified in EIA/TIA-IS-54-B and IS-136) and GSM (Global System for Mobile Communications). Currently, the cellular technology is entering the so called 3rd generation (3G) by means of communication systems such as WCDMA, providing several advantages over the 2nd generation digital systems referred to above.
Many of the advances made in mobile phone technology are related to functional features, such as better displays, more efficient and longer lasting batteries, and means for generating polyphonic ring signals. One functional feature which has become more and more common is built-in cameras. Cameras with video camera functionality are available today in several mobile phones. With the entrance of high bit-rate services, such as EDGE (Enhanced Data-rates for GSM) and 3G, the availability and usability for video-related services will increase. In particular, mobile video telephony, with simultaneous communication of sound and moving images, has recently become commercially available.
For stationary use, video conference systems generally include a camera mounted on or beside a communication terminal, such as a personal computer (PC), or integrated in an internet protocol (IP) enabled phone. Use of such a system may be fairly straightforward, as the user is positioned in front of the terminal with the camera aiming towards the user. However, mobile video conferencing is a bit more cumbersome. The terminal may be positioned in a support unit on a desktop, from which a camera in the unit is aimed towards the object of interest to be captured, typically the user. A more common way of using a mobile phone for video conferencing with face to face transmission is when it is held, such that the built-in camera is manually aimed towards the user. When communicating through a mobile handheld terminal, the user therefore may hold the terminal steady in front of the face so that the receiving party can see the face of the user, i.e. the sending party.
A problem related to video conferencing with a radio terminal is caused by the fact that the built-in camera typically is placed adjacent to and parallel with the display, i.e. the optical axis of the camera is perpendicular to the display surface. The terminal therefore has to be aimed more or less 90° to the face, in order to get a proper image of the user. However, many users find this way of holding the terminal uncomfortable. Furthermore, for most mobile phone designs it may be difficult to use the terminal when placed on a desktop without additional supporting means, since it may require that the user's face be held over the terminal. A related problem is that the terminal may also include a small lamp aimed parallel with the camera to provide light to the object to be captured. When the camera, and the lamp, is aimed towards the face of the user at a 90° angle, there is also a risk that reflections of the user's face in the display surface will disturb the images presented on the display.
Even in the case a camera is configured such that it may be held at an angle to the object to be captured, such as the face of a user of the camera, a problem of image perspective distortion occurs. This may lead to problems when true representation of object dimensions is crucial. For the case of video telephony, the captured image of the user's face will tend to show a wider chin portion compared to the upper part of the face, if the camera is held at a slanted angle away from the face.